A conventional keyless entry system, that is, a system for remotely controlling a door lock, uses a portable device attached to a key to transmit a control signal to a control unit for locking/unlocking a door on a vehicle. The portable device enables a user of the vehicle to lock/unlock the door without inserting the key in a key cylinder.
A modified type of the keyless entry system, that is, a so-called smart entry system, automatically sends out a signal from the portable device to the control unit to unlock the door on the vehicle (refer to a Japanese Patent Document JP-A-H8-270285). In this case, the portable device automatically responds to a detection signal from the control unit on the vehicle, when the portable device reaches within a certain distance from the control unit. A door lock actuator receives a response from the portable device to unlock the door without having an explicit instruction from a user of the vehicle, i.e., a holder of the portable device. In this manner, the modified type of the keyless entry system facilitates a convenience of the user.
Further, a couple of additional features are added to this kind of entry system. For example, the door lock being unlocked when the user touches on a handle, the door lock locked by a press on a button on the handle, a door mirror lamp being lit by itself, a trunk lid opened by a press on a button on the lid, an engine turned on by a press on an ignition switch, and a security system released upon exchange of an ID between the key and the vehicle, are among the features available for the user when he/she approaches the vehicle with the portable device of the smart entry system. In this manner, the user is free from a trouble such as searching the key in a purse and inserting it in a key slot or pressing a button on the portable device for sending an unlock signal. A vehicle equipped with this kind of features is already available.
However, the smart key system does not necessarily improve the convenience of the user when the operation of the portable device is too complicated or an indicator of the device is ambiguous. Further, a confused user sometimes misuses those features to leave the vehicle in a decreased security condition, that is, the user leaves the vehicle in an unlocked condition. Those features also contribute to an increase of battery consumption.
A preventive measure for warning a mis-operation or a lack of operation is already devised in vehicles equipped with the smart entry system. For example, an inconvenience such as a half-shut door and/or a half-released parking brake of a traveling vehicle, or a key or an operating headlight on an unattended vehicle is warned by using an indicator disposed on an instrument panel or a buzzer.
However, the user sometimes fails to respond to the warning because of disturbance of an environment such as a noise or the like. In addition, some user who habitually parks the vehicle in an unlocked condition may feel it a “misplaced warning” when he/she is warned that the vehicle is left unlocked or the like.
Further, the indicator or the buzzer is only effective to the user in a proximity of the vehicle. For example, the vehicle parked away from home will be left unlocked when the user does not notice the warning at the time of departing from the vehicle parked in a parking space.